Actually, the french Panrama [1] invented by Philippe Jaulmes (1958) totally inspired the Imax Dome, after a demo the Expo'67 in Montreal [2]. The Panrama story is long, documents only in french, and I'm still learning bits. For la Géode, the Panrama team tried hard to make a deal to use their french-made tech, so they would have installed 4 smaller omni screens next to the big Imax dome. This was scrapped from the beginning, as la Géode was built on the Omnimax spec from the ground-up. The panrama team still managed to operate a 18m screen in Paris Montparnasse [3] (Espace Gaîté / now Théatre Rive Gauche), and there is one screen left fully equipped in Montpelier, but closed [4]. The Panrama tech was originally 16mm wide, then 35mm, and finally horizontal VistaVision 35mm.

[1] https://fr.m.wikipedia.org/wiki/Panrama [2] https://vimeo.com/199136507 [3] https://www.panrama.net/pages/histoire.html [4] https://www.dailymotion.com/video/x4htqhr